Alright so you have a fine rifle.
There are several methods to work up a load. The basic one that I've always used is to start with a load in your caliber, rounded up to the nearest "10". So a .45 would be 45 grains, rounded up to the nearest 10 would be a starting load of 50 grains of 3Fg. Prime with the same powder. It works fine and keeps things simple.
Shoot that three to five times, from a bench with a rest, at 50 yards (some prefer to start at 25), and then look at your grouping.
Also look at your patch, did it get holes in it? What does the side that was toward the powder in the breech look like.
So..., old-school..., if the rifle is shooting a group (don't worry about the center of the target yet) you increase the powder by 10 to a 60 grain charge, and check the grouping. Try the rifle with 70 grains and also with 80 grains. Did any load stand out as the best group?
So using the best grouping load, you have a companion stand off about 25 yards to the right or left, and you shoot your best grouping load. The person standing off to the side is listening for a distinct "crack" sound as the bullet flies. This means that the load that groups the best is also going super sonic. Now IF it doesn't crack, increase the powder until the crack is heard. IF that load that cracks has acceptable accuracy, THAT's your rifle load.
Now is when you adjust the sights to put the group in the center of the target. Then you try the same load and sight picture on the target at 50 (IF you started at 25), 75, and 100 yards.
Please note, IF you find your rifle shoots much better after the first or second shot, and you will meet guys who stand by the "fouling shot" concept before they load to hunt or target shoot, if you need that, then you patch is too thin.
LD